[1] Univ Warwick, Dept Phys, Coventry CV4 7AL, W Midlands, England
[2] Stockholm Univ, Dept Astron, Oskar Klein Ctr, AlbaNova, SE-10691 Stockholm, Sweden
[3] Aarhus Univ, Dept Phys & Astron, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
[4] Univ Pittsburgh, Dept Phys & Astron, PITT PACC, Pittsburgh, PA 15260 USA
[5] Weizmann Inst Sci, Dept Particle Phys & Astrophys, IL-7610001 Rehovot, Israel
[6] Univ Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark
[7] European Southern Observ, Alonso de Cordova 3107,Casilla 19, Santiago 8320000, Chile
[8] Univ Auckland, Dept Phys, Private Bag 92019, Auckland, New Zealand
[9] Liverpool John Moores Univ, Astrophys Res Inst, IC2, Liverpool Sci Pk,146 Brownlow Hill, Liverpool L3 5RF, Merseyside, England
[10] Max Planck Inst Extraterr Phys, Giessenbachstr, D-85748 Garching, Germany
[11] Univ Andres Bello, Dept Ciencias Fis, Avda Republ 252, Santiago 8320000, Chile
[12] Millennium Inst Astrophys MAS, Nuncio Monsenor Sotero Sanz 100, Santiago 8320000, Chile